Iran has amended its internationally condemned law on stoning convicted adulterers to death to allow judges to impose a different form of execution.

The controversial practice, in which stones are thrown at the partially buried offender until they are dead, has provoked outcries from human rights groups and western countries urging Iran to abandon it.

An article of Iran's Islamic new penal code, released this week, states that, "if the possibility of carrying out the (stoning) verdict does not exist", the sentencing judge may order another form of execution pending final approval by the judiciary chief.

The article does not explain what is meant by the possibility of stoning not existing. Mina Ahadi, of the International Committee Against Stoning, said it proved "international pressure and condemnations" had been effective.

She condemned the revised article as "still being medieval and barbaric", adding: "We believe stoning should be omitted and no other punishment should replace it."

Under Iran's interpretation of Islamic Sharia law in force since its 1979 revolution, adultery is punished by the stoning of convicted adulterers. Women are buried up to their shoulders, but men only up to their waists.

They are spared if they manage to free themselves before dying. Murder, rape, armed robbery and drug trafficking are also punishable by death in Iran, which has one of the highest annual execution counts in the world, alongside China, Saudi Arabia and the US.

In Iran, executions are normally carried out by hanging.

According to Ahadi's group, at least 150 people may have been stoned in Iran since 1980. She said 12 offenders in Iranian jails are currently facing stoning sentences.

According to local media, MPs had removed stoning altogether from the bill that they adopted. But the hardline Guardians Council of clerics and jurists, which must approve all legislation before it goes into force, reinserted it with the amendment.

Stoning was not removed, as it is enshrined in Sharia law, the spokesman for the parliament's judiciary committee, Mohammad Ali Esfandiari, said in April.

The United Nations has urged Iran to ditch stoning as a method of execution, with its experts saying last year that adultery does not constitute a serious crime by international standards. World criticism peaked in 2011 when reports said a married woman, Sakineh Mohammadi Ashtiani, was to be stoned over an "illicit relationship" with two men.

Iran halted the stoning, but Mohammadi Ashtiani, sentenced in 2006, is serving a 10-year sentence on separate charges of complicity in the murder of her husband in a lovers' spat. Her stoning could still be carried out.

In December 2011, a local judicial official said that judiciary chief Ayatollah Sadeq Larijani had decided "to wait to get the view of other religious scholars" before making a final decision.

The last reported case of stoning was in 2009, when an unidentified man was stoned to death in the northern city of Rasht.

That came despite a directive in 2002 by then judiciary chief Ayatollah Mahmoud Hashemi Shahrudi to suspend the practice. His call failed to force any changes to the penal code.

This article appeared in the South China Morning Post print edition as Stoning no longer sole adultery penalty

I thought the US was bad when we signed the declaration of independence but still condoned slavery (not to mention not giving women the vote) That was in the 1800'sNo wonder we regard Iran as a 'backward' country in the 2000' s I hope I am never invited to a cocktail do where the Iranian consul is present.